Other than man, nine-banded armadillos (Dasypus novemcinctus) of the south central United States are the only known highly endemic natural hosts of leprosy. Enzootic infection has occurred for at least 25 years but the origin, range, and risk or armadillo leprosy are not yet known. To clarify these issues, armadillos will be systematically sampled in 4 representative habitats in Louisiana and environmental conditions and population characteristics of the groups will be described. Prevalence of leprosy will be determined by histopathological examination and detection of antibodies to the apparently species-specific phenolic glycolipid-1 (PGL-1) antigen of Mycobacterium leprae. Prevalence rates will be compared between the groups to determine trends in the distribution of disease and indicate factors possibly important in the origin and transmission of enzootic infection. The likelihood that armadillos may serve as a vehicle in the spread of leprosy will be evaluated by examining trophically associated animals for signs of disease. The intensity of infection in representative habitats will be described for later projection and correlation with incidence of human disease. Leprosy indigenous and virgin areas will be examined, naive animals from Florida will be developed as possible epidemiologic sentinels by determining their compatibility in endemic habitats and evaluating their susceptibility to naturally-acquired leprosy infections. A better understand of leprosy in the armadillos will clarify issues of basic scientific importance and may develop these animals as useful models for leprosy research.